The present invention relates to a body structural element consisting of a main body made of fiber-reinforced plastic and a metal connection part, i.e., a so-called hybrid component that consists of at least two different materials, as well as a method for producing such a body structural element for a motor vehicle.
A known body structural element, for example, is a bracing, such as a roof bow, for example, which in the vehicle crosswise direction connects a left roof frame and a right roof frame with one another and therefore produces rigidity of a vehicle body and increases so-called crash resistance of the vehicle body. In known vehicle bodies made of metal, in particular steel, this type of body structural element consists also of metal and is usually fixed to the vehicle body by means of a welded connection or another known connection.
An object of the present invention is to provide a body structural element and a method for producing a body structural element, wherein the body structural element can be produced easily and is lighter while maintaining identical rigidity and strength, and where the body structural element can be connected easily to a traditional vehicle body made of metal or a traditional vehicle body gate made of metal.
This problem is solved by for producing a body structural element, which can be a roof bow, for example, and which has a main body made of fiber-reinforced plastic and a metal connection part, in particular for a motor vehicle, the method including:                Preparation of the metal connection part,        Preparation of a particularly pre-impregnated fiber-plastic matrix semifinished product consisting of a resin system and fibers, wherein the resin system can be a duromer resin system and the fibers in particular can be carbon fibers,        Overlapping configuration of the metal connection part and the fiber-plastic semifinished product in a compression mold,        Compressing the metal connection part with the fiber-plastic matrix semifinished product until a fiber-plastic matrix molding material penetrates into undercuts of the metal connection part, and        Curing or fully reacting the fiber-plastic matrix semifinished product to form the main body made of fiber-reinforced plastic, which is connected in a form-fitting manner to the metal connection part.        
The metal connection part is particularly developed in such a fashion that it can be connected with a metal body structure or a metal body gate, for example by means of welding, gluing, soldering, riveting or screwing.
The method provides an option to connect a metal connection part with said main body in a form-fitting manner already when producing a main body from fiber-reinforced plastic so that a sufficiently permanent, solid and rigid connection between the main body and the metal connection part is created. With the method described, both fibers as well as the plastic matrix can penetrate into the undercut of the metal connection part by means of compression. In other words, fibers can penetrate into the undercut by compression and therefore develop the connection between the main body and the metal connection part to be sufficiently robust.
According to a further development of the method of the present invention, the step of curing, i.e. the complete reaction of the fiber-plastic matrix, is performed by the feeding of heat. The feeding of heat can be carried out by means of the compression mold, for example.
This reduces the number of process steps for producing the body structural element.
According to an advantageous further development of the present invention, the metal connection part is positioned in the overlapping configuration step in the compression mold overlapping between two, in particular pre-impregnated fiber-plastic matrix semifinished products.
By this means it is possible that the fiber-plastic matrix molding material can penetrate into undercuts of the metal connection part from both sides. This advantageously improves a connection between the metal connection part and the main body.
During the compression step, an additional form-closed or frictional connection is advantageously established between the metal connection part and the main body.
Furthermore, during the step of preparing the metal connection part, the metal connection part can be advantageously coated. For this purpose, a cathodic immersion process is used for the coating. By means of said coating, an electrically insulating layer can be formed in an overlapping area between the metal connection part and the main body.
This provides corrosion protection for the metal connection part.
In addition or as an alternative, the coating can also be a layer to promote adhesion, so that in addition to the form-fitting connection between the metal connection part and the main body, it produces an improved material-formed or frictional joint, which further reinforces a connection between the metal connection part and the main body.
Advantageously, during the step of preparing the metal connection part, through holes are introduced in an overlapping area of the metal connection part. For this purpose, the through holes are forming the undercuts of the metal connection part. Through holes can be circular bores. However, the through holes can also have any other suitable form and they can also be introduced into the metal connection part in another manner, for example by punching, laser beam cutting, or milling.
According to a further development of the method, a duromer resin system is used with the fiber-plastic matrix semi-finished product. The duromer resin system can particularly be an unsaturated polyester resin. Preferably, a so-called carbon fiber sheet molding compound (SMC) or a carbon fiber bulk molding compound (BMC) is used.
The fibers can be carbon fibers, but they can also consist of any other suitable fibers, such as glass fibers, for example.
The above-mentioned problem is furthermore solved by a body structural element that is produced by an above-mentioned method according to the present invention. The body structural element according to the present invention comprises at least one main body of fiber-reinforced plastic as well as at least one metal connection part that is connected thereto in a form-fitting manner. The metal connection part has undercuts into which the main body engages.
The main body is preferably a profiled support element. The main body is particularly rigid for this reason and can sufficiently absorb bending moments in various directions.
Preferably, a metal connection part is formed on each end of the main body. The main body preferably has two ends, with a metal connection part being connected to each of said ends.
Consequently, the body structural element can be used for connecting two elements of the body structure or of a body frame.
According to a further development of the body structural element, the main body of which is a profiled support element, the main body has a U-shaped profile. The main body has in particular a U-shaped profile in a section across its longitudinal axis. The main body advantageously has multiple U-profiles that are connected to one another, for example two U-profiles connected to one another. Because a U-profile is an open profile, it can therefore be easily produced with a compression mold made of a fiber-plastic matrix semifinished product.
The metal connection part is preferably a formed metal sheet. The metal sheet can consist of steel or aluminum, for example. The metal sheet is preferably profiled, in particular preferably profiled corresponding to the main body.
According to a further development of the body structural element, the overlapping area of the metal connection part comprises essentially vertical walls and essentially horizontal walls, wherein the undercuts, in particular the through holes, are formed in the vertical walls and/or horizontal walls.
The body structural element is preferably used for connecting to a body structure made of metal and/or to a body gate made of metal by means of the metal connection part. For this purpose, the body structural element is developed such that it stiffens the body structure or the body gate and/or increases a strength of the body structure or the body gate.
The body structural element is preferably a roof bow. A roof bow extends from a left roof frame to a right roof frame in crosswise direction to the vehicle.
To the extent possible, the above-mentioned further developments of the invention can be combined with one another in various ways.
A brief description of the figures follows:
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
An embodiment of the present invention is described below with reference to FIGS. 1 to 4.